Everyone has a gender identity, there are 60+ years of research into gender identity
And like every other body of research you are never going to find a consensus view. For every claim that the vague, nebulous concept of gender exists, there will be another claim against. That’s how social science works, because it simply isn’t possible to theorise a socially-constructed phenomenon using any viable, empirical, scientific formula.
Feminists have spent the best part of the 20th century arguing that their biological destiny is not set in stone because someone (men, usually) has decided for them what amounts to the feminine gender. Eg. pink/blue girl/boy stereotypes amount to nothing more profound than someone else’s (men’s) marketing policy. By the 1980s the primary colours of 70s kids’ toys had given way to the girls’ aisles resembling an explosion in a sugared almond factory. Is this determined by ‘biology?’ The fuck.
Gender is shifting, unstable, and changes its meaning just about every decade. It's a flimsy foundation on which to build a whole identity, that I'll grant you. But this gives no one carte blanche to impose their ideology on others, demand they announce 'their' pronouns, or redefine the language they use to describe themselves without their consent. To those who would try this: who in the actual hell do you think you are?
gender matches your sex.
Not possible. Sex is a set of biological characteristics, 'gender' merely the instrument of women's biological oppression. No wonder so many of us choose not to 'identify' with that. Not least, the human-defined constructs ‘masculinity’ or ‘femininity’ bear no relation to sex, unless they refer to heavy labour or childbearing that are directly linked to these characteristics.
And this also happens to be gender non-conformism. Regardless of how that person presents.